Some data on how it shifts (my experience with my car). You may find it useful.
First to second: minimum 10 km/h.
Second to third: minimum 32 km/h. It may also go into torque converter lock up; depends on throttle opening and the car's mood. Once in lock up, you can go down as low as 1100 rpm before it unlocks.
Third to fourth: minimum 52 km/h. It won't fully lock up until 70 km/h+; once in lockup, you can go down as low as 56 km/h before it unlocks.
At each minimum shift speed, you can lift the pedal momentarily, and re apply pressure. It will upshift. If you don't lift up, it will delay its upshift no matter how light your foot is.
Torque converter lock up is where most of your fuel savings lie. The factors that affect how easily you can go into lockup: engine condition, transmission condition, oil viscosity, tire pressure, and ambient temperature to name a few. You will have to experiment to find out how easily yours will go into lock up.
Another fuel saving tip: don't idle it to warm it up like you would with a carbureted car. Its totally unnecessary, it wastes fuel, and it causes damage to the environment. As soon as you start up, just drive gently while not exceeding 2500 rpm. It will warm up quicker this way. When cold, the car will delay its upshifts, and refuse to go into lockup no matter what.